However, they are limited to linear interpolation of the control point polygon, IIRC.
If you want arbitrary morphing (of the actual curve) you might want to look into implicit curves  represented in geometric algebra . Here  is an example of it.
Packing multiple different fonts into one parametrizable one is the inverse of using one parametrizable font to generate multiple different fonts, right?
>> V-fonts are nice but very limited
As I already mentioned, therefore I agree.
>> Implicit curves are cool but I don't see how they could represent existing font data?
It might not be obvious from the wikipedia page, but implicit curves are not a class of curves but a different way to formalize them (as opposed to parametric curves). So you can think of / deal with the bezier curve segments either as parametric curves or as implicit curves.
That's really damn cool.
When I visit that URL all I get currently is the PDF of the paper?